(1) Field of the Invention
This invention relates to an internal combustion engine, and more particularly to a two-stroke internal combustion engine having an adjustable combustion chamber for varying the compression ratio of the engine, a reciprocating sleeve for controlling gas flow into and out of the combustion chamber, and a turbocharger system for providing air to the engine.
(2) Description of Related Art
Variable compression ratio (VCR) internal combustion engines allow for improved efficiency, and reduced emissions as compared to fixed compression ratio internal combustion engines. The efficiency of the standard engine varies for different loads demanded from the engine. A VCR internal combustion engine allows the volume of the combustion chamber to be adjusted when the load on the engine varies. The volume change allows the engine to operate most efficiently at the highest possible trouble-free compression ratio.
An internal combustion engine operates most efficiently at the highest compression pressure possible without creating problems. This condition can only exist when there is no restriction to the entrance of air into the combustion chamber. Any reduction in the entrance of air into the cylinder, to reduce power or reduce speed, reduces the efficiency of the engine. All engines, except compression ignition engines, with a fixed compression ratio reduce speed and power by increasing the inefficiency of the engine. In an engine having variable compression pressure, the reduction in speed and power can be accomplished without reducing the efficiency of the engine by maintaining maximum possible compression pressure at the highest possible safe level.
There are several different types of variable compression ratio engines described in the prior art. For example, U.S. Pat. No. 2,375,183 issued to Arden discloses a variable compression ratio engine which uses a movable head insert that is placed inside the cylinder over the piston. The size of the compression chamber is automatically controlled by biasing means between the head insert and the cylinder head. The biasing means opposes the compression pressure exerted on the head insert during operation of the engine to control the change of volume of the combustion chamber.
Another type of variable compression ratio internal combustion engine is disclosed in U.S. Pat. No. 4,190,024 issued to Davis. This type of engine uses a flexible fluorocarbon membrane to set the volume of the combustion chamber. The flex of the membrane is controlled by a contra piston and screw mounted in the head of the engine.
A problem with most two-stroke engines is that the exhaust ports remain open even after the inlet ports have closed. This decreases the efficiency of the engine since fuel is allowed to escape through the exhaust ports without having been combusted. These engines pollute the atmosphere with raw fuel.
A two-stroke engine does not have a true suction stroke as do four-stroke engines. Therefore, fuel and air must be forced into the combustion chamber by other means. There are two common ways of forcing air into the combustion chamber. One way uses the upward stroke of the piston to draw air into the crankcase. On the downward stroke of the piston, the air is forced through passages into the combustion chamber. The upward stroke of the piston compresses the air in the combustion chamber. The other way is to have an external source of compressed air connected to the combustion chamber.
One method of increasing the amount of air supplied to an engine is to use a turbocharger. Turbochargers work by using exhaust gases from the engine to drive a compressor which supplies fresh air to the combustion chamber. A standard turbocharger does not operate until the engine is producing exhaust gas. Also, a turbocharger tends to lag behind the air supply requirements of an accelerating engine.